Coated abrasive articles generally comprise a flexible backing material having a coating of abrasive grains on one major surface thereof. Coated abrasive articles typically employ a make coat, for example, a resinous binder, in order to secure the abrasive grains to the backing material, and a size coat, for example, a resinous binder that is applied over the make coat and abrasive grains in order to firmly bond the abrasive grains to the backing material. Flexible backing materials can be cloth, paper, polymeric film, nonwoven materials, vulcanized fiber, and combinations thereof. Although cloth is widely used as a backing material because of strength, heat resistance, and flexibility, cloth has some major disadvantages.
Many known adhesive systems that have been used have low solids content requiring high input for drying and careful selection of backing materials. In the case of solvent-based adhesive, apparatus to extract solvent emissions may also be needed.
For example, cloth backing materials are generally porous, and have to be sealed or treated before a low viscosity make coat layer can be applied, thereby significantly adding to their cost (See, e.g. U.S. Pat. Nos. 2,548,872, 2,658,007 and 4,163,647). Cloth backing material is typically sealed by one or more treatment coats, such as a saturant coat, a presize coat, a backsize coat, or a subsize coat. Such coating saturates the cloth, and results in a stiffer cloth with more body. Alternatively, if the cloth is not previously sealed, the make coat will penetrate into the interstices of the cloth, making the backing material stiff and sometimes brittle, as well as, subsequently applied abrasive grains may not adhere well to the backing material.
In recent years, radiation curable resins have been proposed as cloth treatments or binders for coated abrasives as a substitute for conventional thermally curable resins (See U.S. Pat. No. 4,751,138 and U.S. Ser. No. 07/932,073), however many of these resins suffer the same disadvantages associated with liquid thermally cured liquid resins. Increasing the viscosity of the make coat, that is, increasing the solids content of the make coat, has been one approach to solving the problems associated with directly coating a make coat onto a porous backing material. For example, direct coating of high solid content make coats (such as, hot melt adhesive compositions) typically require elevated temperatures of the backing materials. Some backing materials exhibit such a high surface energy, that the make coat is drawn into the fibers of the backing material, again resulting in a stiff backing material.